Long-term effectiveness of human papillomavirus vaccines among adult women: A real-world scenario

Abstract

Objective: This study aimed to determine the real-world effectiveness of bi- or quadrivalent human papillomavirus (HPV) vaccines in Thai adult women ≥5 years post-vaccination in reducing HPV 16/18-associated low-grade squamous intraepithelial lesions or worse (LSIL+), atypical squamous cells of undetermined significance or worse (ASC-US+), and HPV 16/18 positivity. Methods: A retrospective cohort study was conducted among Thai women aged 20–45 years in Bangkok. The vaccinated and unvaccinated groups were matched according to baseline years. HPV/Pap test results were collected from the medical records and/or obtained by cervical sample collection at the study sites. Adjusted hazard ratios were measured using multivariable Cox regression analyses. Results: A total of 993 participants (493 vaccinated and 500 unvaccinated) were enrolled from 2018 to 2019. The median ages at baseline of the vaccinated and unvaccinated groups were 33 years (interquartile range [IQR] 27–38) and 34 years (IQR 30–38), respectively. The median follow-up periods were 7.3 years (IQR 6.1–8.6) and 7.2 years (IQR 5.8–8.9) for the vaccinated group and the unvaccinated group, respectively. More women in the vaccinated group were single (29.2% vs. 13.2%, P < 0.001) and university graduates (83.2% vs. 75.4%, P = 0.009). The vaccinated and unvaccinated groups had similar personal monthly incomes (>20,000 THB/month, 63.9% vs. 62.4%, respectively, P = 0.685). There were no cases of HPV 16/18-associated LSIL+ in the vaccinated group, whereas there were four cases in the unvaccinated group. HPV vaccine effectiveness was 88.0% (95% CI 2.0–98.5) in the reduction of HPV 16/18-associated ASC-US+, and 84.6% (95% CI 43.5–95.8) in the reduction of HPV 16/18 positivity. Conclusions: HPV vaccine effectiveness was high in adult women in a real-world scenario in a developing country. Free HPV vaccination in adult women in this age group should be further explored when vaccine supplies are not limited. (HPV: human papillomavirus. LSIL+: low-grade squamous intraepithelial lesion or worse. ASC-US+: atypical squamous cells of undetermined significance or worse)